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Abstract:

According to one embodiment, a method includes preliminarily measuring
the amount of overlay or alignment shift of the mark for overlay or
alignment measurement while sequentially shifting a position of a
measurement area relative to the mark for overlay or alignment
measurement so as to position the mark for overlay or alignment
measurement on each of a plurality of partial areas. The measurement area
corresponds to a field angle of the optical measurement system, and an
inside of the measurement area is two-dimensionally divided into the
partial areas. The method includes calculating a tool-induced shift
regarding a characteristic deviation of the optical measurement system
for each of the plurality of partial areas based on a preliminarily
measured result of the amount of overlay or alignment shift. The method
includes determining a partial area to be used from among the plurality
of partial areas on the basis of the tool-induced shift calculated for
each of the plurality of partial areas.

Claims:

1. An overlay or alignment measurement method of measuring an amount of
overlay or alignment shift by acquiring an optical image of a mark for
overlay or alignment measurement formed on a substrate by an optical
measurement system, the overlay or alignment measurement method
comprising: preliminarily measuring an amount of overlay or alignment
shift of the mark for overlay or alignment measurement while sequentially
shifting a position of a measurement area, corresponding to a field angle
of the optical measurement system, relative to the mark for overlay or
alignment measurement so as to position the mark for overlay or alignment
measurement on each of a plurality of partial areas into which an inside
of the measurement area is two-'dimensionally divided; calculating a
tool-induced shift regarding a characteristic deviation of the optical
measurement system for each of the plurality of partial areas based on a
preliminarily measured result of the amount of overlay or alignment
shift; determining a partial area to be used from among the plurality of
partial areas on the basis of the tool-induced shift calculated for each
of the plurality of partial areas; and measuring an amount of overlay or
alignment shift of the mark for overlay or alignment measurement in a
state in which the position of the measurement area relative to the mark
for overlay or alignment measurement is set such that the mark for
overlay or alignment measurement is located on the partial area
determined to be used.

2. The overlay or alignment measurement method according to claim 1,
wherein the measurement area has a size with which plural marks for
overlay or alignment measurement are capable of being present, and the
measurement area is divided into the plurality of partial areas according
to a size of the mark for overlay or alignment measurement.

3. The overlay or alignment measurement method according to claim 1,
wherein the preliminarily measuring includes preliminarily measuring an
amount of overlay or alignment shift of the mark for overlay or alignment
measurement while sequentially shifting the position of the measurement
area in a state in which the substrate is directed in a first direction,
and preliminarily measuring an amount of overlay or alignment shift of
the mark for overlay or alignment measurement while sequentially shifting
the position of the measurement area in a state in which the substrate is
directed in a second direction.

4. The overlay or alignment measurement method according to claim 3,
wherein, the tool-induced shift is calculated, on the basis of the amount
of overlay or alignment shift measured in the state in which the
substrate is directed in the first direction, and the amount of overlay
or alignment shift measured in the state in which the substrate is
directed in the second direction.

5. The overlay or alignment measurement method according to claim 4,
wherein, the tool-induced shift is calculated, by averaging the amount of
overlay or alignment shift measured in the state in which the substrate
is directed in the first direction, and the amount of overlay or
alignment shift measured in the state in which the substrate is directed
in the second direction.

6. The overlay or alignment measurement method according to claim 1,
wherein the tool-induced shift includes an error component regarding coma
aberration of the optical measurement system.

7. The overlay or alignment measurement method according to claim 1,
wherein, a tool matching regarding a deviation amount of the optical
measurement system relative to a reference optical measurement system is
further calculated for each of the plurality of partial areas, based on
the preliminarily measured result of the amount of overlay or alignment
shift.

8. The overlay or alignment measurement method according to claim 7,
further comprising determining whether or not a plurality of overlay or
alignment measurement apparatuses exist, wherein, in a case where one
overlay or alignment measurement apparatus exists, the tool matching is
set to 0, and in a case where a plurality of overlay or alignment
measurement apparatuses exist, the tool matching is calculated, on the
basis of a measured value of an amount of overlay or alignment shift by
the reference optical measurement system of a reference overlay or
alignment measurement apparatus, and a measured value of the amount of
overlay or alignment shift by the optical measurement system.

9. The overlay or alignment measurement method according to claim 8,
wherein, in the case where a plurality of overlay or alignment
measurement apparatuses exist, the tool matching is calculated by
calculating a difference between the measured value of the amount of
overlay or alignment shift by the reference optical measurement system
and the measured value of the amount of overlay or alignment shift by the
optical measurement system.

10. The overlay or alignment measurement method according to claim 1,
wherein, the preliminary measuring includes measuring an amount of
overlay or alignment shift a plurality of times for each of the plurality
of partial areas, and wherein a repeatability regarding reproducibility
of the amount of overlay or alignment shift is further calculated for
each of the plurality of partial areas.

11. The overlay or alignment measurement method according to claim 10,
wherein the repeatability includes an error component in which a
distribution of measured values calculated by measuring the amount of
overlay or alignment shift the plurality of times is associated with a
standard deviation.

12. The overlay or alignment measurement method according to claim 7,
wherein, the preliminary measuring includes measuring an amount of
overlay or alignment shift a plurality of times for each of the plurality
of partial areas, and wherein a repeatability regarding reproducibility
of the amount of overlay or alignment shift is further calculated for
each of the plurality of partial areas.

13. The overlay or alignment measurement method according to claim 10,
wherein, a total measurement uncertainty for each of the plurality of
partial areas is calculated from at least the tool-induced shift and the
repeatability, and wherein a partial area with the smallest total
measurement uncertainty of the plurality of partial areas is determined
as the partial area to be used.

14. The overlay or alignment measurement method according to claim 12,
further comprising determining whether or not a plurality of overlay or
alignment measurement apparatuses exist, wherein, in a case where one
overlay or alignment measurement apparatus exists, a total measurement
uncertainty for each of the plurality of partial areas is calculated from
the tool-induced shift and the repeatability, and in a case where a
plurality of overlay or alignment measurement apparatuses exist, a total
measurement uncertainty for each of the plurality of partial areas is
calculated from the tool-induced shift, the tool matching, and the
repeatability, and wherein a partial area with the smallest total
measurement uncertainty of the plurality of partial areas is determined
as the partial area to be used.

15. An overlay or alignment measurement apparatus measuring an amount of
overlay or alignment shift in a substrate, comprising: an optical
measurement system configured to acquire an optical image of a mark for
overlay or alignment measurement formed on the substrate; a substrate
stage configured to hold the substrate; a measurement controller
configured to control a preliminarily measurement of an amount of overlay
or alignment shift of the mark for overlay or alignment measurement for
each of a plurality of partial areas into which a measurement area
corresponding to a field angle of the optical measurement system is
two-dimensionally divided, while controlling a sequential shift of a
relative position of the measurement area to the mark far overlay or
alignment measurement such that the mark for overlay or alignment
measurement is located on each of the plurality of partial areas; an
operation unit configured to calculate a tool-induced shift regarding a
characteristic deviation of the optical measurement system for each of
the plurality of partial areas, on the basis of the amount of overlay or
alignment shift measured under the control of the measurement controller;
and a determining unit configured to determine a partial area to be used
from among the plurality of partial areas, on the basis of the
tool-induced shift calculated for each of the plurality of partial areas.

16. The overlay or alignment measurement apparatus according to claim 15,
wherein the measurement controller controls to move the substrate stage
so as to position the mark for overlay or alignment measurement on the
partial area determined to be used, and the optical measurement system
acquires the optical image of the mark for overlay or alignment
measurement to perform an overlay or alignment measurement under the
control of the measurement controller.

17. The overlay or alignment measurement apparatus according to claim 15,
wherein the measurement controller controls a measurement of an amount of
overlay or alignment shift of the mark for overlay or alignment
measurement while controlling the sequential shift in a state in which
the substrate is directed in a first direction, and further controls a
measurement of an amount of overlay or alignment shift of the mark for
overlay or alignment measurement while controlling the sequential shift
in a state in which the substrate is directed in a second direction.

18. The overlay or alignment measurement apparatus according to claim 15,
wherein the operation unit further calculates a tool matching regarding a
deviation amount of the optical measurement system relative to a
reference optical measurement system for each of the plurality of partial
areas based on measured amount of overlay or alignment shift.

19. The overlay or alignment measurement apparatus according to claim 15,
wherein the measurement controller controls a measurement of an amount of
overlay or alignment shift a plurality of times for each of the plurality
of partial areas, and the operation unit further calculates a
repeatability regarding reproducibility of an amount of overlay or
alignment shift for each of the plurality of partial areas based on the
amount of overlay or alignment shift measured a plurality of times.

20. The overlay or alignment measurement apparatus according to claim 19,
wherein the operation unit further calculates a total measurement
uncertainty for each of the plurality of partial areas from at least the
tool-induced shift and the repeatability, and the determining unit
determines a partial area with the smallest total measurement uncertainty
of the plurality of partial areas as the partial area to be used.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priority
from the prior Japanese Patent Application No. 2010-212542, filed on Sep.
22, 2010; the entire contents of which are incorporated herein by
reference.

FIELD

[0002] Embodiments described herein relate generally to an
overlay/alignment measurement method and an overlay/alignment measurement
apparatus.

BACKGROUND

[0003] In an image-based overlay measurement apparatus, with the decrease
in the size of a measurement subject device, the requirement for the
accuracy in overlay has intensified. Therefore, the number of sampling
points has been increasing to perform accurate overlay measurement. In a
case of disposing a mark for overlay measurement on a reticle used in a
lithographic process, the mark is disposed on a scribe line in a shot
area. With the heightened demand for the accuracy in overlay measurement,
marks for overlay measurement that need to be disposed in the shot area
are increasing in number. In order to increase the number of marks
disposable on the scribe line, it is necessary to reduce the size of each
mark for overlay measurement.

[0004] The image-based overlay measurement apparatus uses an optical
microscope to perform overlay measurement. Therefore, if the size of the
mark for overlay measurement is reduced, the lens aberration of an
optical microscope is likely to influence the accuracy of overlay
measurement. Specifically, in a case where the optical microscope
(optical measurement system) has comatic aberration which is odd function
aberration, there is a possibility that an optical image of the mark for
overlay measurement will shift, thereby increasing an error of the
overlay measurement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 is a diagram illustrating the configuration of an overlay or
alignment measurement apparatus according to an embodiment;

[0006]FIG. 2 is a flow chart illustrating an overlay or alignment
measurement method according to an embodiment;

[0007] FIGS. 3A to 3E are diagrams illustrating an overlay or alignment
measurement method according to an embodiment;

[0008] FIGS. 4A and 43 are diagrams illustrating an overlay or alignment
measurement method according to an embodiment;

[0009]FIG. 5 is a diagram illustrating an overlay or alignment
measurement method according to an embodiment; and

[0010] FIGS. 6A to 6D are diagrams illustrating an overlay or alignment
measurement method according to a comparative example.

DETAILED DESCRIPTION

[0011] In general, according to one embodiment, there is provided an
overlay or alignment measurement method of measuring an amount of overlay
or alignment shift by acquiring an optical image of a mark for overlay or
alignment measurement formed on a substrate by an optical measurement
system. The method includes preliminarily measuring the amount of overlay
or alignment shift of the mark for overlay or alignment measurement while
sequentially shifting a position of a measurement area relative to the
mark for overlay or alignment measurement so as to position the mark for
overlay or alignment measurement on each of a plurality of partial areas.
The measurement area corresponds to a field angle of the optical
measurement system, and an inside of the measurement area is
two-dimensionally divided into the partial areas. The method includes
calculating a tool-induced shift regarding a characteristic deviation of
the optical measurement system for each of the plurality of partial areas
based on a preliminarily measured result of the amount of overlay or
alignment shift. The method includes determining a partial area to be
used from among the plurality of partial areas on the basis of the
tool-induced shift calculated for each of the plurality of partial areas.
The method includes measuring an amount of overlay or alignment shift of
the mark for overlay or alignment measurement in a state in which the
position of the measurement area relative to the mark for overlay or
alignment measurement is set such that the mark for overlay or alignment
measurement is located on the partial area determined to be used.

[0012] Hereinafter, an overlay or alignment measurement apparatus
according to an embodiment will be described in detail with reference to
the accompanying drawings. The present invention is not limited by this
embodiment.

Embodiment

[0013] An overlay or alignment measurement apparatus 100 according to an
embodiment will be described with reference to FIG. 1. FIG. 1 is a
diagram illustrating the schematic configuration of the overlay or
alignment measurement apparatus 100.

[0015] On the wafer stage 1, a wafer (substrate) WF is mounted.
Specifically, the wafer stage 1 includes a platen (not shown), a coarsely
movable stage (not shown), a finely movable stage (not shown), and a
wafer chuck 2. The platen is fixed to a main body (not shown) of the
overlay or alignment measurement apparatus. The coarsely movable stage is
disposed on the platen and is driven on the platen, for example, in six
directions (an X direction, a Y direction, a Z direction, a rotation
direction around an X axis, a rotation direction around a Y axis, and a
rotation direction around a Z axis). The finely movable stage is disposed
on the coarsely movable stage and is driven on the coarsely movable
stage, for example, in the six directions (the X direction, the Y
direction, the Z direction, the rotation direction around the X axis, the
rotation direction around the Y axis, and the rotation direction around
the Z axis) with a shorter stroke and higher accuracy than the coarsely
movable stage. The wafer chuck 2 is disposed on the finely movable stage
and sticks to the wafer WF when the wafer WF is mounted. In this way, the
wafer stage 1 holds the wafer WF via the wafer chuck 2.

[0016] The wafer WF has the surface on which patterns of a plurality of
layers L1 and L2 are stacked. Further, in the wafer WF including a
plurality of shot areas SH (see FIG. 3A), a plurality of marks for
overlay or alignment measurement (alignment marks) AM1 to AM8 are formed
in each of the shot areas SH. That is, in each shot area SH, as shown in
FIG. 3B, on a scribe line SL around an exposure area ER where a circuit
element pattern will be formed, the plurality of marks for overlay or
alignment measurement AM1 to AM8 are formed.

[0017] Each of the marks for overlay or alignment measurement AM1 to AM8
includes marks of the plurality of layers L1 and L2, and is used to
measure the amount of overlay shift between the layers. For example, as
shown in FIG. 3E, the mark for overlay or alignment measurement AM1
includes marks L1X1 and L1X2 of the layer L1 for measuring an overlay
shift in the X direction, marks L1Y1, L1Y2 of the layer L1 for measuring
an overlay shift in the Y direction, marks L2X1 and L2X2 of the layer L2
for measuring the overlay shift in the X direction, and marks L2Y1 and
L2Y2 of the layer L2 for measuring the overlay shift in the Y direction.

[0018] The driver 12 shown in FIG. 1 receives a control signal from the
controller 13. According to the control signal, the driver 12 drives the
wafer stage 1, for example, in each of the six directions (the X
direction, the Y direction, the Z direction, the rotation direction
around the X axis, the rotation direction around the Y axis, and the
rotation direction around the Z axis). Specifically, the driver 12
includes a first movable element (not shown) provided on one side of the
platen and the coarsely movable stage, a first oscillator (not shown)
provided on the other side of the platen and the coarsely movable stage,
a second movable element (not shown) provided on one side of the coarsely
movable stage and the finely movable stage, and a second oscillator (not
shown) provided on the other side of the coarsely movable stage and the
finely movable stage.

[0019] The controller 13 causes the driver 12 to drive the wafer stage 1
to a predetermined target position.

[0021] The optical prism 8 is disposed among the light source 5, the
optical mirror 6, and the CCD detector 9 on a optical path. The optical
prism 8 functions as a half mirror which permits transmission of the
light emitted from the light source 5 to guide the light to the optical
mirror 6, and reflects light guided from the optical mirror 6 to further
guide the light to the CCD detector 9.

[0022] The optical mirror 6 is disposed between the optical prism 8 and
the optical microscope 7 on the optical path. The optical mirror 6
reflects the light guided from the optical prism 8 so as to guide the
light to the optical microscope 7, and reflects light guided from the
optical microscope 7 so as to guide the light to the optical prism 8.

[0023] The optical microscope 7 is disposed between the optical mirror 6
and the wafer stage 1 on the optical path. The optical microscope 7
includes a lens (not shown) and receives the light guided from the
optical mirror 6 by means of the lens to concentrate the light on the
mark for overlay or alignment measurement AM1 on the wafer WF. Further,
the optical microscope 7 receives light diffracted by the mark for
overlay or alignment measurement AM1 by means of the lens, and forms en
optical image of the mark for overlay or alignment measurement AM1 on an
imaging surface of the CCD detector 9 through the optical mirror 6 and
the optical prism 8.

[0024] A similar process is applied to each of the other marks for overlay
or alignment measurement AM2 to AM8. Further, FIG. 1 exemplarily shows a
case where the optical microscope 7 is an off-axis type provided
independently from an optical projection system (not shown). However, the
optical microscope 7 may be a through-the-lens (TTL) type for performing
overlay or alignment measurement by an optical system through the optical
projection system.

[0025] The CCD detector 9 acquires the optical image formed on the imaging
surface and generates an image signal (analog signal). The COD detector 9
provides the generated image signal to the image processing device 10.

[0026] Further, as long as it is possible to acquire the optical image
formed on the imaging surface, other types of image sensors (for example,
a CMOS image sensor) may be used instead of the CCD detector (COD image
sensor) 9.

[0027] The image processing device 10 receives the image signal from the
CCD detector 9. The image processing device 10 performs predetermined
analog signal processing on the received image signal and then performs
analog-to-digital conversion processing on the processed image signal
(analog signal) so as to generates an image signal (digital signal).
Then, the image processing device 10 performs predetermined digital
signal processing on the image signal (digital signal) so as to generate
image data, calculates data (waveform data) necessary for overlay or
alignment measurement from the image data through image processing such
as edge detection or the like, and provides the waveform data to the
process operation device 11. Further, the image processing device 10
provides the image data to the process operation device 11.

[0028] The process operation device 11 receives the waveform data and the
image data from the image processing device 10. On the basis of the
waveform data, the process operation device 11 calculates the amount of
overlay shift between the layers.

[0029] Next, the internal configurations and operations of the controller
13 and the process operation device 11 will be described.

[0030] The controller 13 includes a measurement controller 13a and a
storage unit 13b.

[0031] The measurement controller 13a selects, for example, seven shot
areas SH (shot areas shown in FIG. 3A by diagonal lines) from the
plurality of shot areas SH in the wafer WF, as shot areas SH for overlay
or alignment measurement, and drives the wafer stage 1 with the driver 12
so as to position an optical axis of the optical microscope 7 in one shot
area SH selected from the seven shot areas SH.

[0032] Then, the measurement controller 13a selects a mark for overlay or
alignment measurement (for example, AM1) to be used for overlay or
alignment measurement, from the plurality of marks for overlay or
alignment measurement AM1 to AM8 in the shot area SH, and causes the
driver 12 to drive the wafer stage 1 so as to position the optical axis
of the optical microscope 7 in the selected mark for overlay or alignment
measurement AM1. That is, the measurement controller 13a causes the
driver 12 to drive the wafer stage 1 so as to position the mark for
overlay or alignment measurement AM1 in the measurement area as shown in
FIG. 3B by a broken line.

[0033] Specifically, the measurement area is an area corresponding to the
field angle of the optical microscope 7, and is, for example, a
rectangular area (area shown in FIGS. 4A and 4B by broken lines)
corresponding to a measurement view of the optical microscope 7. The
measurement area includes, for example, a plurality of partial areas A1
to A5, B1 to B5, C1 to C5, D1 to D5, and E1 to E5, each being a fraction
obtained by two-dimensionally dividing the inside of the measurement
area, as shown in FIG. 30. That is, the inside of the Measurement area is
two-dimensionally divided according to the size of the marks for overlay
or alignment measurement. For example, in a case where the size of the
measurement area is 50 μm×50 μm and the size of each mark for
overlay or alignment measurement is 10 μm×10 μm, the inside
of the measurement area is divided into 5×5 partial areas.

[0034] Further, the partial areas do not need to be completely separated
from each other but may overlap each other. For example, the measurement
area may be divided such that the partial areas overlap each other by
half of the size of the mark, like a case where the measurement field
angle is 50 the size of the mark is 10 μm, and the number of partial
areas is 10×10.

[0035] The measurement controller 13a sequentially causes the driver 12 to
drive the wafer stage 1 to position the mark for overlay or alignment
measurement AM1 on each of the plurality of partial area A1 to E5.
Specifically, the measurement controller 13a causes the driver 12 to
rotate the wafer stage 1 around the Z axis so as to direct a notch (a
notched portion of the wafer WF) downward (see FIG. 4A), and then moves
the wafer stage 1 in the X direction and the Y direction to position the
mark AM1 on each of the partial areas A1 to E5. Further, the measurement
controller 13a causes the driver 12 to rotate the wafer stage 1 180
degrees around the Z axis from the state in which the notch is directed
downward (see FIG. 4A), so as to direct the notch upward (see FIG. 4B).
In the state in which the notch is directed upward (see FIG. 4B), the
measurement controller 13a causes the driver 12 to move the wafer stage 1
in the X direction and the Y direction so as to position the mark for
overlay or alignment measurement AM1 on each of the partial areas A1 to
E5. In this way, with respect to the state in which the notch is directed
upward and the state in which the notch is directed downward, the
measurement controller 13a preliminarily control measurement of the
amount of overlay or alignment shift of the mark for overlay or alignment
measurement AM1 for each of the plurality of partial areas A1 to E5 a
plurality of times while sequentially shifting the relative position of
the measurement area to the mark AM1 for overlay or alignment
measurement.

[0036] For example, with respect to each of the state in which the notch
is directed downward (see FIG. 4A) and the state in which the notch is
directed upward (see FIG. 4B), the measurement controller 13a causes the
driver 12 to drive the wafer stage 1 so as to position the mark for
overlay or alignment measurement AM1 on the partial area A1 as shown in
FIG. 3D by a solid line. In this way, the measurement controller 13a
preliminarily control measurement of the amount of overlay or alignment
shift of the mark for overlay or alignment measurement AM1 for the
partial area A1 the plurality of times.

[0037] For example, with respect to each of the state in which the notch
is directed downward (see FIG. 4A) and the state in which the notch is
directed upward (see FIG. 4B), the measurement controller 13a causes the
driver 12 to drive the wafer stage 1 so as to position the mark for
overlay or alignment measurement AM1 on the partial area 31 as shown in
FIG. 3D by a broken line. In this way, the measurement controller 13a
preliminarily control measurement of the amount of overlay or alignment
shift of the mark for overlay or alignment measurement AM1 for the
partial area B1 the plurality of times.

[0038] For example, with respect to each of the state in which the notch
is directed downward (see FIG. 4A) and the state in which the notch is
directed upward (see FIG. 4B), the measurement controller 13a causes the
driver 12 to drive the wafer stage 1 so as to position the mark for
overlay or alignment measurement AM1 on the partial area A1 as shown in
FIG. 3D by a dashed-dotted line. In this way, the measurement controller
13a preliminarily control measurement of the amount of overlay or
alignment shift of the mark for overlay or alignment measurement AM1 for
the partial area C1 the plurality of times.

[0039] For example, with respect to each of the state in which the notch
is directed downward (see FIG. 4A) and the state in which the notch is
directed upward (see FIG. 4B), the measurement controller 13a causes the
driver 12 to drive the wafer stage 1 so as to position the mark for
overlay or alignment measurement AM1 on the partial area E5 as shown in
FIG. 3D by a dashed-two dotted line. In this way, the measurement
controller 13a preliminarily control measurement of the amount of overlay
or alignment shift of the mark for overlay or alignment measurement AM1
for the partial area E5 the plurality of times.

[0040] The storage unit 13b stores an overlay or alignment measurement
recipe. The overlay or alignment measurement recipe includes a
measurement condition and a measurement process of a case of performing
overlay or alignment measurement.

[0041] The process operation device 11 includes an operation unit 11a and
a determining unit 11b.

[0042] The operation unit 11a calculates a tool-induced shift for each of
the plurality of partial areas A1 to E5, on the basis of the amount of
overlay or alignment shift preliminarily measured with respect to each of
the state in which the notch is directed downward (see FIG. 4A) and the
state in which the notch is directed upward (see FIG. 4B) under the
control of the measurement controller 13a as described above. The
tool-induced shift is an error component regarding a deviation in the
characteristic of the optical microscope (optical measurement system) 7.
For example, the tool-induced shift (TIS) is an error component regarding
coma aberration of the lens (not shown) in the optical microscope. For
example, the operation unit 11a calculates each of the TIS(A1) to TIS(E5)
of the plurality of partial areas A1 to E5 (see FIG. 5).

[0043] Specifically, with respect to each of the partial areas A1 to E5,
if the amount of overlay or alignment shift measured in the state in
which the notch is directed downward is E(0), and the amount of overlay
or alignment shift measured in the state in which the wafer rotates
180° around the Z axis from the state in which the notch is
directed downward (the notch is directed upward) is E (180), the
operation unit 11a calculates the TIS by the following Equation 1.

TIS={E(0)+E(180)}/2 (Equation 1)

[0044] Further, the operation unit 11a calculates repeatability for each
of the plurality of partial areas A1 to E5, on the basis of the amount of
overlay or alignment shift preliminarily measured the plurality of times
under the control of the measurement controller 13a as described above
(see FIG. 5). The repeatability is an error component regarding the
reproducibility of the amount of overlay or alignment shift. For example,
the repeatability (Rep) is an error component in which a distribution of
the measured values calculated by measuring the amount of overlay or
alignment shift the plurality of times is 3σ (three times a
standard deviation). For example, the operation unit 11a calculates each
of Rep(A1) to Rep(E5) of the plurality of partial areas A1 to E5 (see
FIG. 5).

[0045] Further, the operation unit 11a calculates a tool matching for each
of the plurality of partial areas A1 to E5, on the basis of an amount of
overlay or alignment shift measured by a reference optical measurement
system (not shown) in advance, and the amount of overlay or alignment
shift preliminarily measured under the control of the measurement
controller 13a as described above. The reference optical measurement
system is an optical measurement system provided to a reference overlay
or alignment measurement apparatus (apparatus No. 1). For example,
information on the amount of overlay or alignment shift measured by the
reference optical measurement system may be inquired to and received from
the reference overlay or alignment measurement apparatus via a
communication line through a communication interface (not shown), or may
be input by a user through a user interface (not shown). The tool
matching is an error component regarding a deviation amount of the
measurement controller 13a relative to the reference optical measurement
system. For example, the tool matching (Mat) is expressed by a difference
between a measured value of the amount of overlay or alignment shift by
the reference optical measurement system and a measured value of the
amount of overlay or alignment shift by the measurement controller 13a in
the case of measuring the same mark for overlay or alignment measurement.
For example, the operation unit 11a calculates each of Mat(A1) to Mat(E5)
of the plurality of partial areas A1 to E5 (see FIG. 5).

[0046] Further, in a case where there is only one overlay or alignment
measurement apparatus, that is, in a case where there is only one overlay
or alignment measurement apparatus with an optical measurement system,
the Mat is 0.

[0047] Furthermore, the operation unit 11a calculates a total measurement
uncertainty from at least the tool-induced shift and the repeatability,
as a determination indicator of the accuracy of measurement for each of
the plurality of partial areas A1 to E5 (see FIG. 5). The total
measurement uncertainty is a total error in overlay or alignment
measurement. For example, the total measurement uncertainty (TMU) is
calculated by totally combining the above-mentioned individual error
components in overlay or alignment measurement.

[0048] Specifically, when measured values of the TIS, the Rep, and the Mat
for each of the partial areas A1 to E5 are TIS, Rep, and Mat,
respectively, the operation unit 11a calculates the TMU by the following
Equation 2.

[0049] The TMU is an indicator corresponding to each of the TIS, the Rep,
and the Mat.

[0050] Further, in a case where there is only one overlay or alignment
measurement apparatus, that is, in a case where there is only one overlay
or alignment measurement apparatus with an optical measurement system,
the Mat is 0. Therefore, the operation unit 11a calculates the TMU by the
following Equation 3.

[0051] The determining unit 11b determines a partial area with the
smallest total measurement uncertainty (TMU) from the plurality of
partial areas A1 to E5, as a partial area to be used. For example, in a
case where the TMU(E5) is the smallest among the total measurement
uncertainties TMU(A1) to TMU(E5) corresponding to the plurality of
partial areas A1 to E5, the determining unit 11b determines the partial
area E5 corresponding to the TMU(E5) as the partial area to be used. The
determining unit 11b provides information on the partial area to be used
to the controller 13.

[0052] Therefore, the controller 13 receives the information on the
partial area to be used from the determining unit 11b, and updates the
overlay or alignment measurement recipe stored in the storage unit 13b
according to the information on the partial area to be used. Then, when
measuring the amount of overlay shift between the layers, the measurement
controller 13a drives the wafer stage 1 so as to position the mark for
overlay or alignment measurement on the partial area determined to be
used (for example, the partial area E5) (for example, such that a
relative position relationship shown in FIG. 3D by the dashed-two dotted
line is established) with reference to the updated overlay or alignment
measurement recipe stored in the storage unit 13b. Therefore, the
measurement controller 13a causes the drive 12 to shift the relative
position of the measurement area to the mark for overlay or alignment
measurement so as to position the mark for overlay or alignment
measurement on the partial area determined to be used, and then controls
measurement of the amount of overlay or alignment shift of the mark for
overlay or alignment measurement.

[0053] Next, an overlay or alignment measurement method according to an
embodiment will be described with reference to FIG. 2. FIG. 2 is a flow
chart illustrating an overlay or alignment measurement method according
to an embodiment.

[0054] In step S1, the controller 13 receives an overlay or alignment
measurement start command and starts an overlay or alignment measurement
process. The overlay or alignment measurement start command may be input
by a user through a user interface (not shown), or may be input from a
controller of an exposing device (not shown) or an external controller
via a communication line through a communication interface (not shown).

[0055] In step S2, the controller 13 determines whether the overlay or
alignment measurement recipe is used for the first time or not, with
reference to the overlay or alignment measurement recipe stored in the
storage unit 13b. In a case where the overlay or alignment measurement
recipe is used for the first time (Yes in step S2), the controller 13
proceeds to perform step S3. In a case where the overlay or alignment
measurement is not used for the first time (No in step S2), the
controller 13 proceeds to perform step S22.

[0056] In step S3, the measurement controller 13a of the controller 13
causes the driver 12 to rotate the wafer stage 1 around the Z axis so as
to direct the notch (a mark corresponding to a notched portion of the
wafer WF) downward (in a direction of 0°) (see FIG. 4A).

[0057] In step S4, the measurement controller 13a controls measurement of
the repeatability in the partial areas A1, B1, C1, D1, and E1 of the
measurement area in the state in which the notch is directed downward.

[0058] Specifically, in the state in which the notch is directed downward,
the measurement controller 13a sequentially causes the driver 12 to move
the wafer stage 1 in the X direction and the Y direction to position the
mark for overlay or alignment measurement AM1 on each of the partial
areas A1, B1, C1, D1, and E1 of the measurement area. While sequentially
causing the driver 12 to shift the relative position of the measurement
area to the mark for overlay or alignment measurement AM1 in that way,
the measurement controller 13a preliminarily controls measurement of the
amount of overlay or alignment shift of the mark for overlay or alignment
measurement AM1 for each of the partial areas A1, B1, C1, D1, and E1 with
respect to the state in which the notch is directed downward a plurality
of times.

[0059] On the basis of the amount of overlay or alignment shift
preliminarily measured a plurality of times by control of the measurement
controller 13a, the operation unit 11a calculates the repeatability for
each of the partial areas A1, B1, C1, D1, and E1 (see FIG. 5). For
example, the repeatability Rep is an error component in which a
distribution of the measured values calculated by measuring the amount of
overlay or alignment shift the plurality of times is 3σ (three
times a standard deviation).

[0060] For example, the operation unit 11a calculates each of the Rep(A1),
Rep(B1), Rep(C1), Rep(D1), and Rep(E1) of the plurality of partial areas
A1, B1, C1, D1, and E1 (see FIG. 5).

[0061] In step S5, the measurement controller 13a controls measurement of
the amount of overlay or alignment shift of the mark for overlay or
alignment measurement AM1 a plurality of times for the partial areas A2,
B2, C2, D2, and E2 of the measurement area in the state in which the
notch is directed downward, similar to step S4, and the operation unit
11a calculates (measures) the repeatability by performing calculation
similar to step S4.

[0062] In step S6, the measurement controller 13a controls measurement of
the amount of overlay or alignment shift of the mark for overlay or
alignment measurement AM1 a plurality of times for the partial areas A3,
B3, C3, D3, and E3 of the measurement area in the state in which the
notch is directed downward, similar to step S4, and the operation unit
11a calculates (measures) the repeatability by performing calculation
similar to step S4.

[0063] In step S7, the measurement controller 13a controls measurement of
the amount of overlay or alignment shift of the mark for overlay or
alignment measurement AM1 a plurality of times for the partial areas A4,
B4, C4, D4, and E4 of the measurement area in the state in which the
notch is directed downward, similar to step S4, and the operation unit
11a calculates (measures) the repeatability by performing calculation
similar to step S4.

[0064] In step S8, the measurement controller 13a controls measurement of
the amount of overlay or alignment shift of the mark for overlay or
alignment measurement AM1 a plurality of times for the partial areas A5,
B5, C5, D5, and E5 of the measurement area in the state in which the
notch is directed downward, similar to step S4, and the operation unit
11a calculates (measures) the repeatability by performing calculation
similar to step S4.

[0065] In step S9, the measurement controller 13a causes the driver 12 to
rotate the wafer stage 1 180° around the Z axis from the state in
the notch is directed downward (in the direction of 0°) so as to
direct the notch upward (in a direction of 180°) (see FIG. 4B).

[0066] In step S10, the measurement controller 13a controls measurement of
the amount of overlay or alignment shift of the mark for overlay or
alignment measurement AM1 a plurality of times for the partial areas A1,
E1, C1, D1, and E1 of the measurement area in the state in which the
notch is directed upward, similar to step S4, and the operation unit lie
calculates (measures) the repeatability by performing calculation similar
to step S4.

[0067] In step S11, the measurement controller 13a controls measurement of
the amount of overlay or alignment shift of the mark for overlay or
alignment measurement AM1 a plurality of times for the partial areas A2,
B2, C2, D2, and E2 of the measurement area in the state in which the
notch is directed upward, similar to step S4, and the operation unit 11a
calculates (measures) the repeatability by performing calculation similar
to step S4.

[0068] In step S12, the measurement controller 13a controls measurement of
the amount of overlay or alignment shift of the mark for overlay or
alignment measurement AM1 a plurality of times for the partial areas A3,
B3, C3, D3, and E3 of the measurement area in the state in which the
notch is directed upward, similar to step S4, and the operation unit 11a
calculates (measures) the repeatability by performing calculation similar
to step S4.

[0069] In step S13, the measurement controller 13a controls measurement of
the amount of overlay or alignment shift of the mark for overlay or
alignment measurement AM1 a plurality of times for the partial areas A4,
B4, C4, D4, and E4 of the measurement area in the state in which the
notch is directed upward, similar to step S4, and the operation unit 11a
calculates (measures) the repeatability by performing calculation similar
to step S4.

[0070] In step S14, the measurement controller 13a controls measurement of
the amount of overlay or alignment shift of the mark for overlay or
alignment measurement AM1 a plurality of times for the partial areas A5,
B5, C5, D5, and E5 of the measurement area in the state in which the
notch is directed upward, similar to step S4, and the operation unit 11a
calculates (measures) the repeatability by performing calculation similar
to step S4.

[0071] In step 15, the operation unit 11a of the process operation device
11 calculates the tool-induced shift for each of the plurality of partial
areas A1 to E5 from the measured results of the amount of overlay or
alignment shift in the state in which the notch is directed downward
(steps S4 to S8) and the measured results of the amount of overlay or
alignment measurement in state in which the notch is directed upward
(steps 10 to 14) (see FIG. 5). For example, the tool-induced shift(TIS)
is an error component regarding the coma aberration of the lens (not
shown) in the optical microscope.

[0072] Specifically, with respect to each of the partial areas A1 to E5,
if the amount of overlay or alignment shift measured in the state in
which the notch is directed downward is E(0), and the amount of overlay
or alignment shift measured in the state in which the wafer rotates
180° around the Z axis from the state in which the notch is
directed downward (the notch is directed upward) is E (180), the
operation unit 11a calculates the TIS by Equation 1. In this way, the
operation unit lie calculates, for example, each of the TIS(A1) to
TIS(E5) of the plurality of partial areas A1 to E5 (see FIG. 5).

[0073] In step S16, the operation unit 11a determines whether there are a
plurality of overlay or alignment measurement apparatuses or not. The
operation unit 11a may obtain the information on whether there is another
overlay or alignment measurement apparatus or not by inquiring of another
overlay or alignment measurement apparatus and receiving the response,
for example, via a communication line through a communication interface
(not shown), or may obtain the information on whether there is another
overlay or alignment measurement apparatus or not by the input of the
user through a user interface (not shown). In a case where another
overlay or alignment measurement apparatus does not exist, that is, there
is only one overlay or alignment measurement apparatus (No in step S16),
the operation unit lie proceeds to perform step 17. In a case where
another overlay or alignment measurement apparatus exists, that is, there
are a plurality of overlay or alignment measurement apparatuses (Yes in
step S16), the operation unit 11a proceeds to perform step S18.

[0074] In step S17, the operation unit 11a calculates the total
measurement uncertainty as the determination indicator of the accuracy of
measurement for each of the plurality of partial areas A1 to E5, from the
tool-induced shift (TIS) and the repeatability (Rep) (see FIG. 5). For
example, the total measurement uncertainty (TMU) is calculated by totally
combining the above-mentioned individual error components in overlay or
alignment measurement.

[0075] Specifically, when measured values of the TIS and the Rep for each
of the partial areas A1 to E5 are referred to as TIS and Rep,
respectively, the operation unit 11a calculates the TMU by Equation 3.

[0076] In step S18, the operation unit 11a calculates the tool matching
for each of the plurality of partial areas A1 to E5, on the basis of the
amount of overlay or alignment shift measured by the reference optical
measurement system (not shown) and calculated in advance, and the amount
of overlay or alignment shift preliminarily measured under the control of
the measurement controller 13e as described above. The reference optical
measurement system is the optical measurement system provided to the
reference overlay or alignment measurement apparatus (apparatus No. 1).
Information on the amount of overlay or alignment shift measured by the
reference optical measurement system may be acquired by questioning the
reference overlay or alignment measurement apparatus via a communication
line through a communication interface (not shown), or may be user's
input through a user interface (not shown).

[0077] For example, the tool matching (Mat) is expressed by the difference
between the measured value of the amount of overlay or alignment shift by
the reference optical measurement system and the measured value of the
amount of overlay or alignment shift by the measurement controller 13a in
the case of measuring the same mark for overlay or alignment measurement.
For example, the operation unit 11a calculates each of Mat (A1) to Mat
(E5) of the plurality of partial areas A1 to E5 (see FIG. 5).

[0078] In step S19, the operation unit 11a calculates the total
measurement uncertainty as the determination indicator of the accuracy of
measurement for each of the plurality of partial areas A1 to E5, from the
tool-induced shift (TIS), the repeatability (Rep), and the tool matching
(Mat) (see FIG. 5). For example, the total measurement uncertainty (TMU)
is calculated by totally combining the above-mentioned individual error
components in overlay or alignment measurement.

[0079] Specifically, when measured values of the TIS, the Rep, and the Mat
for each of the partial areas A1 to E5 are referred to as TIS, Rep, and
Mat, respectively, the operation unit 11a calculates the TMU by Equation
2.

[0080] In step S20, the determining unit 11b determines (decides) a
partial area with the smallest total measurement uncertainty (TMU) of the
plurality of partial areas A1 to E5, as the partial area to be used. For
example, in a case where the TMU(E5) is the smallest among the total
measurement uncertainties TMU(A1) to TMU(E5) of the plurality of partial
areas A1 to E5, the determining unit 11b determines the partial area E5
corresponding to the TMU(E5), as the partial area to be used. The
determining unit lib provides information on the partial area to be used
to the controller 13.

[0081] In step S21, the controller 13 receives the information on the
partial area to be used from the determining unit 11b, and updates the
overlay or alignment measurement recipe stored in the storage unit 13b
according to the information on the partial area to be used.

[0082] In step S22, the measurement controller 13a of the controller 13
causes the driver 12 to drive the wafer stage 1 so as to position the
mark for overlay or alignment measurement AM1 on the partial area
determined to be used (for example, the partial area E5) (for example,
such that a relative position relationship shown in FIG. 3D by the
dashed-two dotted line is established) with reference to the updated
overlay or alignment measurement recipe stored in the storage unit 13b
when measuring the amount of overlay shift between the layers. Therefore,
in the state where the measurement controller 13a causes the driver 12 to
shift the relative position of the measurement area to the mark for
overlay or alignment measurement AM1 so as to position the mark for
overlay or alignment measurement AM1 on the partial area determined to be
used in advance, the optical microscope 7 acquires an optical image of
the mark for overlay or alignment measurement AM1 and performs
measurement of the amount of overlay or alignment shift of the mark for
overlay or alignment measurement AM1.

[0083] Further, the above-mentioned process is similar in the case of
using any another of other marks for overlay or alignment measurement AM2
to AM8 of the plurality of marks for overlay or alignment measurement AM1
to AM8 in the shot area SH to perform overlay or alignment measurement.
The above-mentioned process is performed again in a case where the used
mark for overlay or alignment measurement is changed. Further, the
above-mentioned process is performed for every lithographic process in a
method of manufacturing a semiconductor device, every overlay or
alignment measurement apparatus, every shot area used for overlay or
alignment measurement, and every mark for overlay or alignment
measurement. The partial area determined in step S20 to be used may be
common to shot areas on the same wafer, or may depend on shot areas on
the same wafer.

[0084] Here, consider a case where the size of each mark for overlay or
alignment measurement AM101, AM102, AM103, or AM104 in a shot area 100 is
the almost same as the size of measurement area corresponding to the
field angle of the optical microscope 7 as indicated by a broken line in
FIG. 6A. The size of the coma aberration of the lens of the optical
microscope 7 has a distribution (location dependency) in the measurement
area as shown in FIG. 6D. For example, in a case shown in FIG. 6D, in the
measurement area, the influence of the coma aberration is greatest in a
white area ranging from a top right corner to a bottom left corner, and
the influence of the coma aberration decreases toward a dark grey area
ranging from the bottom right corner or the top left corner (as the color
is deepened). In this case, as shown in FIG. 6B, the size of the mark for
overlay or alignment measurement AM101 is the almost same as the size of
the measurement area and the mark for overlay or alignment measurement
AM101 extends both over the area greatly influenced by the coma
aberration and the area little influenced by the coma aberration.
Therefore, in a case of measuring the amount of overlay shift between the
layers by using the mark for overlay or alignment measurement AM101,
there is a tendency that the influence of the coma aberration is averaged
so that the influence of the coma aberration on the accuracy of overlay
or alignment measurement is small. However, since the size of the marks
for overlay or alignment measurement AM101 to 104 is large, the number of
marks for overlay or alignment measurement disposable on a scribe line
SL100 (around an exposure area ER100) in a shot area SH100 is limited (to
4 in a case of FIG. 6A).

[0085] In contrast, in the embodiment, as shown in FIGS. 3B and 3D, the
size of marks for overlay or alignment measurement AM1 to AM8 in the shot
area SH is considerably smaller than the size of the measurement area.
Therefore, it is possible to easily increase the number of (8 in a case
of FIG. 3B) marks for overlay or alignment measurement disposable on the
scribe line SL in the shot area SH, and to increase the number of
sampling points. Accordingly, it is possible to improve the accuracy of
overlay or alignment measurement.

[0086] Also, consider a case in which the size of the mark for overlay or
alignment measurement is considerably smaller than the size of the
measurement area and overlay or alignment measurement is performed in a
state in which the mark for overlay or alignment measurement is always
located in the center of the measurement area as shown in FIG. 6C. In
this case, as shown in FIGS. 6C and 6D, the mark for overlay or alignment
measurement is located in the area greatly influenced by the coma
aberration. Therefore, in a case of measuring the amount of overlay shift
between the layers by using the mark for overlay or alignment
measurement, there is a possibility that an optical image of the mark for
overlay or alignment measurement shifts by the coma aberration so as to
increase an error of the overlay or alignment measurement.

[0087] In contrast, in the embodiment, in steps S1 to S14, preliminary
overlay or alignment measurement is performed while the relative position
between the mark for overlay or alignment measurement and the measurement
area sequentially shifts so as to position the mark for overlay or
alignment measurement on each of the plurality of partial areas A1 to E5
into which the inside of the measurement area is two-dimensionally
divided. In step S15, the TIS (tool-induced shift) regarding the coma
aberration (characteristic deviation) of the lens of the optical
microscope (optical measurement system) 7 is calculated for each of the
partial areas A1 to E5. In step S20, the partial area (for example, the
partial area E5) in which the indicator corresponding to the TIS
(tool-induced shift) is smallest is determined as the partial area to be
used. In step S22, the mark for overlay or alignment measurement is
located on the partial area determined in step S20 and overlay or
alignment measurement is performed. Therefore, as shown in FIGS. 3C and
6D, it is possible to perform overlay or alignment measurement in a state
in which the mark for overlay or alignment measurement is located on a
partial area, least influenced by the coma aberration, in the measurement
area. As a result, even in a case where the size of the mark for overlay
or alignment measurement is considerably smaller than the size of the
measurement area, it is possible to reduce the influence of the coma
aberration on the accuracy of overlay or alignment measurement, and thus
to improve the accuracy of the overlay Or alignment measurement.

[0088] Further, in the embodiment, in step S18, the Mat (tool matching)
regarding the difference (deviation amount) between the measured value of
the amount of overlay or alignment shift by the optical microscope
(optical measurement system) 7 and the measured value of the amount of
overlay or alignment shift by the reference optical microscope (reference
optical measurement system) is calculated for each of the partial areas
A1 to E5. Therefore, in step 319, it is possible to calculate the TMU
(total measurement uncertainty) by adding the Mat (tool matching).
Accordingly, it is possible to perform overlay or alignment measurement
in a state in which the mark for overlay or alignment measurement is
located on a partial area, least influenced by the coma aberration and
the Mat (tool matching), in the measurement area. As a result, it is
possible to reduce the influence of the coma aberration and the tool
matching on the accuracy of overlay or alignment measurement. Even from
this point, it is possible to improve the accuracy of the overlay or
alignment measurement.

[0089] Furthermore, in the embodiment, in steps S1 to S14, the amount of
overlay or alignment shift is measured a plurality of times and the Rep
(repeatability) regarding the distribution of the measured values
calculated by measuring the amount of overlay or alignment shift a
plurality of times (the reproducibility of the amount of overlay or
alignment shift) is calculated for each of the partial areas A1 to E5.
Therefore, in step S19, it is possible to calculate the TMU (total
measurement uncertainty) by adding the repeatability. Accordingly, it is
possible to perform overlay or alignment measurement in a state in which
the mark for overlay or alignment measurement is located on a partial
area, least influenced by the coma aberration and the repeatability, in
the measurement area. As a result, it is possible to reduce the influence
of the coma aberration and the repeatability on the accuracy of overlay
or alignment measurement. Even from this point, it is possible to improve
the accuracy of the overlay or alignment measurement.

[0090] Moreover, in the embodiment, in a case where there is only one
overlay or alignment measurement apparatus and it is possible to set the
Mat (tool matching) to 0, in step S17, the TMU (total measurement
uncertainty) for each of the partial areas A1 to E5 is calculated from
the TIS (tool-induced shift) and the Rep (repeatability). In a case where
there are a plurality of overlay or alignment measurement apparatuses, in
step S19, the TMU (total measurement uncertainty) for each of the partial
areas A1 to E5 is calculated from the TIS (tool-induced shift), the Rep
(repeatability), and the Mat (tool matching). Therefore, in step S20, it
is possible to calculate the total measurement uncertainty of the overlay
or alignment measurement by considering all of the tool-induced shift,
the repeatability, and the tool matching. Accordingly, it is possible to
perform overlay or alignment measurement in a state in which the mark for
overlay or alignment measurement is located on a partial area, in which
the total influence of the coma aberration, the repeatability, and the
tool matching is smallest, in the measurement area. As a result, it is
possible to reduce the total influence of the coma aberration, the
repeatability, and the tool matching on the accuracy of overlay or
alignment measurement. Even from this point, it is possible to improve
the accuracy of the overlay or alignment measurement.

[0091] While certain embodiments have been described, these embodiments
have been presented by way of example only, and are not intended to limit
the scope of the inventions. Indeed, the novel embodiments described
herein may be embodied in a variety of other forms; furthermore, various
omissions, substitutions and changes in the form of the embodiments
described herein may be made without departing from the spirit of the
inventions. The accompanying claims and their equivalents are intended to
cover such forms or modifications as would fall within the scope and
spirit of the inventions.

Patent applications by Kazutaka Ishigo, Mie JP

Patent applications in class With registration indicia (e.g., scale)

Patent applications in all subclasses With registration indicia (e.g., scale)